Explanatory Note 



!rtie series embodies results of investigations, usually of 

 restricted scope, intended to aid or direct management or 

 utilisation practices and as guides for administrative or 

 legislative action* It is isstied in limited quantities for the 

 official use of Federal, State or cooperating agencies and in 

 processed form for economy and to avoid delay in publication* 



Washington, D. C« 

 January 1950 



